This invention relates generally to a subsea wellhead connection assembly for establishing fluid communication and production capability between a subsea wellhead and an adjacent subsea atmospheric manifold system. In particular, the invention relates to such a connection assembly for use in a subsea well completion system for handling oil and/or gas production from multiple offshore template-drilled wells, as well as methods for installing the connection assembly in a subsea well completion system. In addition to the recovery of hydrocarbons, the present invention also relates to the recovery of subaqueous deposits of sulfur and other minerals from beneath the seas. The invention likewise relates to wells used to inject water or hydrocarbon gases into subterranean hydrocarbon reservoirs.
Bottom-supported, permanent surface installations have, in the past, proven to be economically and technologically feasible in comparatively shallow waters to recover hydrocarbon fluids from subaqueous formations. In deeper waters, such as several hundred to several thousand meters, utilization of such surface installations must be limited to very special situations. Installations extending above the water surface are disadvantageous, even in shallower water, where there are adverse surface conditions, such as ice loading.
Recent developments in the offshore oil and gas industry extend production to more undersea areas, such as the outer fringes of the continental shelves and the continental slopes, utilizing a system of submerged, template-drilled wellheads and a submerged well completion system. Subsea systems are feasible for installing multiple wellheads in relatively close proximity through the use of a drilling template secured on the marine floor. Such systems can be operated from remote, floating surface facilities using electrohydraulic control systems, with the subsea systems being connected to the surface facilities by flowlines for production fluids, injection fluids, hydraulic controls, electric cable, and the like.
Habitable, subsea atmospheric work enclosures, or satellites, can be maintained adjacent to multiple, template-drilled wellheads for housing operating and/or maintenance personnel, as disclosed, for example, in U.S. Pat. No. 3,556,208 (Dean). In such systems, the subsea satellite is independently connected to a number of surrounding subsea wellheads and serves to control the production from, and maintenance of, the wellheads. The wells are drilled in a circular pattern through a template on the marine floor, the template serving also as a base upon which the satellite is installed. The production/control passages of each of the wells are connected to production equipment such as a manifold within the satellite by separate wellhead connection assemblies which are independently lowered into place from a surface vessel and form portions of the flow paths between the wellheads and the production manifold within the satellite.
While the aforementioned subsea satellite systems prove generally satisfactory in water depths of about 100 to 150 meters, the use of such systems at depths on the order of 300 to 750 meters presents certain problems. For example, the utilization of guidelines and diver assistance for subsea installation of the components of the system becomes more complex with increasing water depths. In waters of such substantial depth, it becomes necessary to employ dynamic guidance systems, including remote television and/or sonar monitoring, during the installation process. Also, subsea installation of wellhead connection assemblies in prior art well completion systems presents problems in terms of guidance of the assemblies into operative position between the wellhead and the satellite, particularly at water depths approaching 750 meters. Furthermore, prior art subsea well completion systems typically utilize submerged satellite hulls having vertically arranged hull penetrators to provide fluid access to the interior of the satellite. Such an arrangement of penetrators produces undesirable hull stress conditions, particularly at depths in excess of 150 meters.
Additionally, prior art subsea wellhead connection assemblies are typically of such a large size that they are difficult to handle during subsea installation and are vulnerable to damage both during and after installation. Prior assemblies having a curved flowline loop projecting up from the top of the satellite are particularly susceptible to damage.
It is an objective of the present invention to overcome the problems and disadvantages of the prior art by providing an improved subsea wellhead connection assembly significantly reduced in size and capable of simplified installation between a subsea wellhead and a subsea atmospheric work enclosure, for establishing fluid communication between the wellhead and a manifold system contained within the subsea work enclosure. It is a further objective of the present invention to provide improved structural protection for wellhead connection assemblies and the subsea work enclosure.
Additional objectives and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and advantages of the invention will be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the objectives and in accordance with the purposes of the invention, as embodied and broadly described herein, the invention comprises a subsea wellhead connection assembly for establishing fluid communication and production capability between a subsea wellhead and an adjacent subsea manifold system, comprising: (1) conduit means for fluidly connecting the wellhead and the manifold system, the conduit means having one end extending substantially horizontally and the other end situated below the horizontal end; (2) wellhead connector means fluidly connected to said other end of the conduit means for releasably connecting the conduit means to the wellhead upon downward movement of the assembly to establish fluid communication therebetween; (3) manifold system connector means fluidly connected to the horizontal end of the conduit means for releasably connecting the conduit means to the manifold system upon lateral movement of the manifold system connector means to establish fluid communication therebetween; and (4) a guide frame rigidly secured to the wellhead connector means for supporting the manifold system connector means and the conduit means, and for vertically aligning the wellhead connector means over the wellhead and horizontally aligning the manifold system connector means with the manifold system.
The invention additionally comprises a subsea wellhead connection assembly for establishing fluid communication and production capability between a manifold system situated within a subsea work enclosure and an adjacent subsea wellhead located in a generally wedge-shaped well bay, comprising: (1) conduit means for fluidly connecting the wellhead and the manifold system, the conduit means having one end extending substantially horizontally and the other end extending downwardly; (2) wellhead connector means fluidly connected to the downwardly directed end of the conduit means for releasably connecting the conduit means to the wellhead upon downward movement of the assembly to establish fluid communication therebetween; (3) manifold system connector means fluidly connected to the horizontal end of the conduit means for releasably connecting the conduit means to the manifold system upon lateral movement of the manifold system connector means to establish fluid communication therebetween; and (4) a guide frame rigidly secured to the wellhead connector means for supporting the manifold system connector means and the conduit means, and for vertically orienting the wellhead connector means over the wellhead and horizontally aligning the manifold system connector means with the manifold system, wherein two opposing sides of the guide frame are wedge-shaped similarly to the wedge-shaped well bay for providing the desired orientation and alignment of the wellhead connection assembly as it is moved laterally during its installation over the wellhead.
The wellhead connection assembly of the present invention, as further embodied and described herein, comprises a subsea wellhead connection assembly for establishing fluid communication and production capability between a subsea wellhead and an adjacent subsea atmospheric manifold system and for establishing fluid communication between the wellhead and a connector mandrel, comprising: (1) first conduit means curved in a loop traversing at least about one full turn for fluidly connecting the wellhead and the manifold system, the first conduit means having one end extending substantially horizontally and the other end situated below the horizontal end; (2) wellhead connector means fluidly connected to said other end of the first conduit means for releasably connecting the first conduit means to the wellhead upon downward movement of the assembly to establish fluid communication therebetween; (3) manifold system connector means fluidly connected to the horizontal end of the first conduit means for releasably connecting the first conduit means to the manifold system upon lateral movement of the manifold system connector means to establish fluid communication therebetween, the manifold system connector means having a pair of guide pins extending substantially horizontally from opposing sides of the connector means to permit alignment during horizontal movement of said manifold system connector means; (4) substantially vertically extending second conduit means having a downwardly directed end fluidly connected to the wellhead connector means and an upwardly directed end fluidly connected to the connector mandrel for establishing fluid communication between the wellhead and the mandrel independent of the manifold system connector means; (5) a protective guide frame comprised of rigid structural piping for supporting and surrounding the manifold system connector means and the first and second conduit means, and for vertically aligning the wellhead connector means over the wellhead and horizontally aligning the manifold system connector means with the manifold system, the guide frame comprising upper and lower support members having substantially identical outer peripheries, when viewed from above, and vertical tubular members rigidly connected between the upper and lower support members, the lower support member being rigidly attached to the wellhead connector means and the upper support member being rigidly attached to the upwardly directed end of the second conduit means; (6) mechanical linkage means supported by the guide frame and having a lever arm having one end attached to the manifold system connector means for laterally moving the manifold system connector means into operative connection with the manifold system, and for reversing such operation to disconnect, the mechanical linkage means preferably having an actuating member pivotally connected to the lever arm, the actuating member having its free end extending substantially vertically upward; and (7) a pair of substantially oppositely facing guide plates rigidly attached to at least one of the vertical members of the guide frame, each guide plate having a slot for supporting and guiding the respective manifold system connector guide pins during lateral movement of the manifold system connector means, the guide pins, guide plates and slots being relatively situated so as to align the manifold system connector means with the manifold system.
As embodied and broadly described herein, the invention further comprises a method of establishing fluid communication and production capability between a marine floor wellhead and an adjacent subsea manifold system, comprising the steps of: (1) providing a wellhead connection assembly comprising conduit means for fluidly connecting the wellhead and the manifold system, the conduit means having one end extending substantially horizontally and the other end situated below the horizontal end, wellhead connector means fluidly connected to said other end of the conduit means, manifold system connector means fluidly connected to the horizontal end of the conduit means, and a guide frame rigidly secured to the wellhead connector means for supporting the manifold system connector means and the conduit means; (2) lowering the wellhead connection assembly; (3) vertically aligning the wellhead connector means over the wellhead and horizontally aligning the manifold system connector means with the manifold system; (4) releasably connecting the wellhead connector means to the wellhead, thereby establishing fluid communication between the wellhead and the conduit means; and (5) then horizontally moving the manifold system connector into operative connection with the manifold system, thereby establishing fluid communication between the conduit means and the manifold system.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and, together with the description, serve to explain the principles of the invention.